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The present invention relates generally to radio frequency and microwave circulators, and more specifically to a junction-type stripline circulator providing enhanced mechanical and electrical performance with a reduced cost of manufacture.
Radio Frequency (RF) and microwave circulators are known that employ a DC-biasing magnetic field generated in ferrite material enveloping a conductor to provide at least one non-reciprocal transmission path between signal ports on a network. A conventional junction-type stripline circulator comprises at least one junction configured as an interface between the signal ports. Each junction of the junction-type stripline circulator typically includes two (2) permanent magnets, two (2) ground plane portions disposed between the magnets, two (2) ferrite disks disposed between the ground plane portions, a dielectric constant medium disposed between the ferrite disks, and a conductor sandwiched between the ferrite disks and patterned to correspond to the transmission paths between the signal ports. The permanent magnets are configured to generate a DC-biasing magnetic field in the ferrite disks, thereby providing the desired non-reciprocal operation of the transmission paths between the signal ports on the network.
One drawback of the conventional junction-type stripline circulator is that it frequently provides inconsistent electrical performance. For example, a junction-type stripline circulator having four (4) signal ports typically comprises two (2) junctions disposed between the four (4) ports, in which each junction includes respective pluralities of magnets and ferrite disks and respective conductors. Further, the two (2) junctions of the 4-port stripline circulator are typically interconnected by a microstrip transmission line.
However, because the conventional 4-port junction-type stripline circulator comprises the two (2) interconnected junctions that include the respective pluralities of permanent magnets and ferrite disks, the DC-biasing magnetic fields generated by the respective magnets are frequently non-uniform. Further, the dielectric constant media disposed between the respective ferrite disk pairs also tend to be non-uniform. As a result, the desired non-reciprocal operation of the 4-port junction-type stripline circulator is sometimes difficult to achieve.
Moreover, because each junction comprises a respective stack of components including the permanent magnets, the ground plane portions, the ferrite disks, and the conductors, the number of parts included in the junction-type stripline circulator increases with the number of junctions of the circulator. This can significantly increase costs associated with handling and assembling multi-junction stripline circulators. Further, having respective stacks of components for each junction in the junction-type stripline circulator can cause uneven tolerance build-up in the component stacks, which can adversely affect stripline circulator performance.
It would therefore be desirable to have a junction-type stripline circulator that can be used in RF and microwave applications. Such a junction-type stripline circulator would be configured to provide enhanced mechanical and electrical performance, while reducing the costs of handling and assembly.
In accordance with the present invention, a junction-type stripline circulator is provided in which electrical and mechanical performance is enhanced while handling and assembly costs are reduced. Benefits of the presently disclosed invention are achieved by configuring the junction-type stripline circulator to include an oval permanent magnet and an oblong ferrite component that can be employed by more than one junction of the circulator.
In one embodiment, the junction-type stripline circulator comprises a compact multi-element cascade circulator including a plurality of junctions connected in cascade to provide a plurality of non-reciprocal transmission paths between signal ports on a network. The plurality of junctions comprises a single oval permanent magnet, an oblong ground plane disposed near the permanent magnet, a ferrite component including two (2) oblong ferrite elements disposed near the ground plane, and a conductor sandwiched between the ferrite elements. A dielectric constant medium is disposed between the two (2) ferrite elements. Further, the conductor is patterned to correspond to the configuration of the transmission paths between the signal ports. The multi-element cascade circulator further includes a metal housing having an open top into which the plurality of adjacent junctions is disposed, and a metal cover configured to enclose the top of the housing to secure the adjacent junctions therein. The metal housing has a plurality of slots through which respective contact terminals of the conductor protrude to make contact with the signal ports on the network.
The plurality of adjacent junctions further comprises two (2) oval pole pieces associated with the permanent magnet, and an oval cover return component. A first oval pole piece is disposed between the magnet and the ground plane, and a second oval pole piece is disposed between the base of the housing and the multi-ferrite component. The cover return component is disposed between the cover and the permanent magnet.
In this embodiment, the combination of the ground plane, the multi-ferrite component, and the conductor forms a Radio Frequency (RF) or microwave circuit configured to provide desired non-reciprocal transmission paths between the network signal ports. Further, the combination of the pole pieces, the permanent magnet, the metal housing, the cover return component, and the metal cover forms a magnetic circuit configured to generate a DC-biasing magnetic field in the multi-ferrite component, thereby achieving the desired non-reciprocal operation of the transmission paths. Moreover, the two (2) pole pieces are configured to enhance the homogeneity of the magnetic field in the multi-ferrite component, and the cover return component is configured to provide an easy return path for the magnetic flux associated with the DC-biasing magnetic field from the ferrite elements to the permanent magnet.
By configuring the compact multi-element cascade circulator to include the oval permanent magnet and the oblong ferrite component that can be employed by more than one junction of the circulator, the circulator achieves numerous benefits. For example, the performance of the multi-element cascade circulator is enhanced. Particularly, the electrical performance of the circulator is more consistent because the dielectric constant medium between the junctions is uniform throughout the RF or microwave circuit. Other benefits include reduced insertion loss, more consistent return loss values, more uniform DC-biasing magnetic fields, better power handling due to improved distribution of heat in the oblong ferrite component, reduced tolerance build-up because the oblong ferrite component eliminates an air line interface that typically exists in conventional multi-junction-type stripline circulator configurations, simpler and easier fixturing and assembly because fewer parts are involved and critical transformer positions are eliminated, lower overall costs because fewer parts are handled in stockrooms and during assembly, lower total material costs due to the combining of parts and the reduction of part quantities, and quicker and more uniform magnetic field settings because the oval permanent magnet design allows the use of a c-coil degausser, which generally cannot be used with conventional junction-type stripline circulator designs.
Other features, functions, and aspects of the invention will be evident from the Detailed Description of the Invention that follows.